Surgical invasion of the body generally results in trauma and to an accumulation of fluids from the traumatized tissue itself or from the circulatory system. To avoid the build-up of pressure and to minimize the danger of infection, it is desirable that such fluids be removed from the surgical site. Accidentally inflicted wounds also are subject to similar fluid build-ups, and will heal faster if the excess fluids are drained and are prevented from re-accumulating. In such cases, it is common practice to install a drain tube designed for this purpose, and to leave this tube in place to provide for continuous fluid removal until the accumulation has abated.
A variety of drainage tubes or catheters have been devised for removing excess fluids from postsurgical sites or wounds. Such drains often employ external grooves to collect the fluids, or contain perforations through which fluids can enter a central passageway that carries the fluids away from the site. In many cases, suction is applied to the external end of the tube to aid in the fluid removal. One problem with existing drainage tubes and catheters is that when a drainage device is left in place for any length of time, tissue often grows into the drain, especially into its perforations, thus hindering and rendering very painful the drain's eventual removal from the body. Thus, an optimal drain design is one that efficiently removes unwanted fluids, but that minimizes the tendency of tissues to grow into the drain. Previous drain designs have approached these goals in different ways.
U.S. Pat. No. 5,360,414 provides a drain having a circular internal passageway and several externally extending portions whose walls curve inwardly to form a number of relatively small external lumens that run lengthwise along the external surface of the drain. The curved walls forming the lumens do not quite meet, thus providing a groove-like opening into which fluid can enter. The drain itself is interrupted by several perforations that are large enough to intersect more than one of the external lumens, and that provide a means for fluid enter the central passageway.
U.S. Pat. No. 4,650,463 describes a tube for surgical drainage that has an internal passageway formed in a clover-leaf cross-section, and that has an external channel formed by outwardly extending portions of the tubing wall that curve towards each other to form the channel. Perforations located at the bottom of the external lumen connect the lumen with the internal passageway to provide for fluid flow into the internal passageway of the tube.
U.S. Pat. No. 4,573,965 discloses a drain tube with smooth exterior walls and having two lumens, and which is perforated at one end. This drain features an antibacterial filter and a check valve that are mounted in-line within the second lumen.
U.S. Pat. No. 4,543,089 provides a drain consisting of a thick walled tube having two closed lumens situated entirely within the wall, one of which is used for feeding fluids into the body or wound, the other of which is used for aspiration.
U.S. Pat. No. 4,531,935 describes an aspiration cannula assembly for use during heart surgery in delivering cardioplegic fluid to and aspirating air from the aorta. The device provides an inner cannula for delivering fluids, which is enclosed within an outer cannula that has a plurality of holes through which air can be aspirated.
U.S. Pat. No. 4,465,481 describes a wound drain catheter having a drain segment, a transition tube segment, and an extrusion tube segment. The drain segment lacks a central passageway, but provides several external longitudinal channels that are formed by outwardly projecting extruding portions of the tube.
U.S. Pat. No. 4,445,897 discloses a surgical drain catheter that has a central passageway and one or more external slots or lumens that extend longitudinally along the catheter. Perforations located at the bottom of the external lumens connect them to the central passageway of the main tube to provide for fluid flow.
U.S. Pat. No. 3,771,527 discloses a surgical drain comprising inner and outer tubes, one within the other, which are arranged so that fluid can be introduced through one tube into the body cavity while suction is simultaneously applied to remove excess fluids from the site through the other tube. The inner wall of the outer tube is equipped with inwardly extending ribs to prevent its collapse against the inner tube. Both the inner and outer tubes are perforated to allow for the flow of fluids.
U.S. Pat. No. 3,599,641 discloses a catheter having multiple internal lumens that provide a principal channel and one or more secondary channels, with an opening through the sidewall of the catheter at the proximal end to provide access to the secondary channel.
U.S. Pat. No. 3,020,913 discloses a surgical drain comprising a flexible tube with an inner and outer wall. An inlet means is provided by holes between the two walls, which connect the passage to the outside of the tube at one location to let fluid drain into the passage. The outlet means comprises an axial slit that extends through the tube between the walls, and is designed so that the slit is closed when the tube is compressed on both walls. Thus, the slit will open to let fluid escape from the passage when the pressure inside the passage exceeds the external pressure on the outside walls of the tube.
U.S. Pat. No. 1,596,754 describes a surgical drain designed to resist collapsing by virtue of two pair of internally located ribs that run longitudinally inside the internal passageway of the smooth-surfaced drain tube.
U.S. Pat. No. 2,930,378 describes an abdominal drain tube, closed at one end, consisting of flexible inner and outer tubes, one running within the other, both tubes being perforated.
U.S. Pat. No. 1,045,326 discloses a flexible irrigating catheter closed at one end and designed for introducing fluids into body cavities, and for causing a return flow of the irrigating liquid on the exterior of the catheter. This catheter has an internal passageway and also has external open U-shaped channels arranged longitudinally along its exterior surface, the channels being designed to provide for the return flow of the irrigating fluid. Perforations situated at the bottoms of the open channels connect the channels with the internal passageway.
Despite the above-described approaches to providing drains or catheters for removing excess fluid from the body, there has remained a need for new and improved methods for such drainage, particularly methods that minimize or eliminate the problem of occlusion of the drain by debris in a wound or the ingrowth of living tissue surrounding the wound during the time it is left in place.